A time-to-digital converter (Time-to-Digital Converter, TDC) is a timer for converting time intervals into digital signals. The time-to-digital converter has wide application in the field of time measurement, including measurement of flight time, a phase detector in a phase-locked loop, a data converter, high-speed signal capture, a demodulator and other measurement or instrument application. The main objective of designing the TDC is to improve the resolution and provide a large dynamic range. A differential chain may realize a resolution smaller than a gate-level delay, and an annular TDC occupies a small area and has a large dynamic range.
There are two methods for realizing the TDC by using the differential chain in the prior art: A, a two-step method, namely time is coarsely measured and then measured by using the differential chain; and B, an annular differential structure is adopted, information including a coarse value, a fine value, an in-circle position and the like is recorded during measurement, and a measurement result is obtained by operation.
However, in the method A of the prior art, an additional measurement circuit is needed, so that the occupied area is too large and the structure is relatively complex; and the method B is only realized by using the annular structure, is skilful but complex in calculation, and involves multiple parameters.